"Activation" or "priming" is the biochemical process that controls the ability of macrophages to produce microbicidal oxygen radicals like superoxide anion (O2-). Activated macrophages produce more O2- when they are "triggered" by microbes or by chemical stimuli like phorbol ester or f-met-leu-phe. Therefore, activated macrophages are better able to control infection. Activated macrophages also secrete more IL-1 and TNFalpha, which cause inflammation, bone resorption, fever, and cachexia. Macrophages are activated in vivo by infection, or they can be "primed" in vitro by exposure to lipopolysaccharide (LPS), muramyl dipeptide or interferon-gamma(IFN-gamma). IL-1 and TNFalpha also prime macrophages. The goal of this project is to understand the mechanisms involved in activation and priming. The first specific aim is to examine the effects of a powerful inhibitor of priming, sulfatide from Mycobacterium tuberculosis, on O2-- release and secretion of monokines in human monocytes. The purpose is to understand how a successful pathogen can block the normal priming pathway that prepares macrophages to kill bacteria. Preliminary evidence suggests that sulfatide blocks priming for enhanced O2-release by LPS and IFN-gamma, but augments secretion of IL-1beta. In this way, sulfatide may prevent the mycobacteria from being killed, while promoting granuloma formation and tissue destruction. The second aim is to investigate the receptors involved in priming by LPS. Because only a few molecules of LPS are needed to prime monocytes, detection of the LPS receptor has been difficult. The possibility that Mac-1 membrane glycoprotein is the LPS receptor will be tested using monocytes from Mac-1 deficient patients. The possibility of a plasma membrane or intracellular receptor for LPS, or for an LPS-lipoprotein complex, will be examined by electron microscopy and affinity chromatography. The third aim is to examine the signal transduction pathway controlling LPS priming. The involvement of G proteins, phospholipases and lipocortin, cytosolic Ca2+, protein phosphorylation, and translocation will be examined. The fourth aim is to examine how LPS affects the regulation of gene expression for NADPH oxidase (the enzyme system that produces O2-), and for IL-1 and TNFalpha. Cytochrome b, a membrane-associated component of NADPH oxidase, will be studied to determine if its concentration, sub-cellular distribution or participation in electron transport is affected by priming. Two cytosolic components of the oxidase will also be examined. The effect of primers and inhibitors on the transcription, stability and translation of mRNA for IL-1 and TNFalpha will be determined. Knowledge of the mechanisms involved in priming monocytes will permit development of stratagems and drugs to improve killing of pathogens by macrophages, and to suppress inflammation caused by macrophages and their products. Such agents should help to limit tissue destruction in periodontal disease and in other chronic infections and inflammatory diseases.